1. Field of the Invention
This is a partial oxidation process. More particularly it pertains to preheating and starting-up a free-flow refractory lined partial oxidation gas generator for the production of gas streams comprising H.sub.2 and CO.
2. Description of the Prior Art
Processes for the partial oxidation of liquid or solid fuels have been disclosed (cf. Ullmann's Encyklopadie der technischen Chemie, 3rd Edition, 1965, Volume 16, under the heading "Synthesegas", pages 589-635, and Supplementary Volume, 3rd Edition, 1970, under the heading "Ammonia", pages 458-480). With regard to the patent literature, reference may in particular be made to the following German Pat. Nos. 1,061,303; 1,080,079; 1,170,379; 1,905,604; and 2,162,253; and to the following coassigned U.S. Pat. Nos. 2,928,460; and 3,874,592.
The above publications show that because of the rather high temperature in the reaction zone and because of the impurities in the starting material (above all, heavy residual oils and solid fuels containing ash-producing constituents, e.g. vanadium, nickel and iron), problems arise specifically in relation to the burner, also to the reactor lining, and to the temperature-measuring instruments located therein. These problems frequency lead to interruptions of the operation. It is true that in recent years it has been possible to improve the life of the burners from initially only a few hours to from 20 to 30 days and then to the currently usual average value of from 60 to 70 days. However, shutting off the gasifier part of the production installation can also be necessitated by faults and corrosion problems in upstream or downstream parts of the installation (e.g. pumps, waste heat boilers, gas scrubbers or shift conversion units) or by a power failure.
Unless such faults are dealt with rapidly (without about 1 hour), the reaction zone cools to the point at which restarting the gas production is not directly feasible.
Restarting after a fault lasting longer than at most 1 hour then entails the following as does the first start-up: To heat (or reheat) the reaction zone, a special "preheat burner" of very simple construction is employed, consisting essentially of a pipe through which a fuel gas passes and which is of such dimensions that with the amounts of fuel gas involved, a stable flame forms at the pipe orifice. The air required for the combustion of the fuel gas reaches this flame from its enviroment, without a special device and without the use of pressure. In general, it is advantageous to reduce the pressure slightly in the reaction zone and thereby draw in the amount of air required, and transport the combustion gases through the reaction zone.
As may be seen from the above, the preheat burner is not firmly fixed to the upper orifice of the reaction zone, through which the main burner is normally introduced, and instead is merely placed over this orifice by means of a simple device. Accordingly, the main process burner must be removed if the reaction zone requires reheating. When the ignition temperature specified for the particular starting material has been exceeded by means of the preheat burner, the latter is removed and the main burner is fixed. During the time it takes for changing burners and fixing the main burner; and during other work required to start the reaction, e.g. the start-up of pumps, the temperature in the reaction zone drops substantially, so that reliable ignition is only possible if the above manipulations can be carried out very rapidly. If there are any delays and if, as a consequence, the temperature falls below a limiting value specified for safety reasons and depending on the nature of the fuel to be gasified, ignition is no longer feasible. Instead, it is necessary in such cases -- which are not particularly rare -- to remove the main burner again and to reheat the reaction zone with the preheat burner yet again.